Polyethylene resin expanded molded products are excellent in flexibility and in heat insulating property. Therefore, the polyethylene resin expanded molded products are used for various purposes as shock-absorbing packing materials and heat insulating materials.
As a method of producing a polyethylene resin expanded molded product, in-mold expanding and molding has been known in which (i) a mold is filled with expanded particles obtained by pre-expanding polyethylene resin particles with use of a foaming agent such as a butane gas (bead expansion) and (ii) the expanded particles are heated, by introducing a heating medium, such as steam, into the mold, so that the expanded particles are fused to each other. In the bead expansion, a crosslinked polyethylene resin has been used as a raw material of a molded product because expanded particles which have a high expansion ratio and which are excellent in heat resistance are easily obtained. Meanwhile, it has been proposed to produce, with use of a non-crosslinked polyethylene resin, a molded product which is good in moldability (see Patent Literatures 1 and 2).
As a foaming agent used in such a field, a volatile organic foaming agent has been conventionally used because expanded particles having a high expansion ratio are obtained (see Patent Literatures 1 and 2). However, due to an increase in concern for environmental issues, an inorganic gas, such as a carbon dioxide gas, has come to be used as the foaming agent in recent years (see Patent Literatures 3 and 4).
Furthermore, in recent years, expanded polyethylene resin particles containing an antistatic agent have been used as a raw material of a polyethylene resin expanded molded product so that the polyethylene resin expanded molded product has an antistatic property. For example, Patent Literature 5 discloses obtaining a polyethylene resin expanded molded product by expanding and molding, in a mold, expanded polyethylene resin particles that have an expansion ratio of 15 times to 30 times and that have been obtained by expanding, with use of a carbon dioxide gas serving as a foaming agent, polyethylene resin particles which contain 0.1 parts by weight of a nucleating agent, 1.0 part by weight of a polyhydric alcohol fatty acid ester serving as an antistatic agent, and 0.2 parts by weight of a hydrophilic compound, relative to 100 parts by weight of a linear low-density polyethylene and each of which has a weight of 4.5 g.
Meanwhile, Patent Literature 6 discloses obtaining a polyethylene resin expanded molded product by expanding and molding, in a mold, expanded polyethylene resin particles that have an expansion ratio of 15 times to 30 times, that have an appropriate shrinking property, and that have been obtained by expanding, with use of a carbon dioxide gas serving as a foaming agent, polyethylene resin particles which contain 0.04 parts by weight of a nucleating agent, 1 part by weight to 2 parts by weight of a polyhydric alcohol fatty acid ester serving as an antistatic agent, and 0.2 parts by weight to 0.5 parts by weight of a hydrophilic compound and each of which has a weight of 1.3 g.
However, according to those techniques, in a case where such an expanded molded product which is obtained from expanded polyethylene resin particles having a high expansion ratio is made thin, there is room for improvement in fusibility of expanded polyethylene resin particles.